Kojiro Shimada  1,2, Akinori Takami3, Takatsugu Ishida2, Yuta Taniguchi2, Shuichi Hasegawa4, Chak K. Chan5, Yong Pyo Kim1,6,7, Neng-Huei Lin1,8, Shiro Hatakeyama1,2

1 Global Innovation Research Organization, Tokyo University of Agriculture and Technology, Tokyo, Japan
2 Institute of Agriculture, Graduate School of Tokyo University of Agriculture and Technology, Tokyo, Japan
3 National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki, Japan
4 Center for Environmental Science in Saitama, Kazo, Saitama, Japan
5 School of Energy and Environment, City University of Hong Kong, Hong Kong, China
6 Department of Chemical Engineering & Materials Science, Ewha Womans University, Seoul, Korea
7 Department of Environmental Science & Engineering, Ewha Womans University, Seoul, Korea
8 National Central University, Chung-Li, Taiwan

Received: August 5, 2020
Revised: April 29, 2021
Accepted: May 6, 2021

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.200505  

Cite this article:

Shimada, K., Takami, A., Ishida, T., Taniguchi, Y., Hasegawa, S., Chan, C.K., Kim, Y.P., Lin, N.H., Hatakeyama, S. (2021). Long-term Measurements of Carbonaceous Aerosol at Cape Hedo, Okinawa, Japan: Effects of Changes in Emissions in East Asia. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.200505


  • The annual average concentration of EC did not change between 2004 and 2013.
  • The annual average concentration of OC decreased at the rate of 0.11 μg C m−3 yr−1.
  • Fossil fuel combustions contribute more to OC and EC than biomass burning.
  • Large contribution of fossil fuel combustions were shown by emission inventories.


We investigated changes in sources of carbonaceous aerosol and their effect on long-term trends in elemental carbon (EC) and organic carbon (OC) concentrations at the Cape Hedo Atmosphere and Aerosol Monitoring Station (CHAAMS) in Okinawa, Japan, for the period 2004–2013. EC and OC concentrations were measured by using a semi-real-time carbon monitor and performing an offline filter analysis involving the thermal-optical method, following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. Overall, the annual average concentration of EC did not change between 2004 and 2013, whereas the OC concentration clearly decreased at the rate of 0.11 μg C m−3 yr−1 (α > 0.05). The secondary OC (SOC)/OC ratio showed an increasing trend from 2004 till 2011, and the high value of this ratio is possibly due to a reduction in primary emissions of OC and changes in the composition of organic compounds emitted in China. In spring and winter, air pollutants were frequently transported from China. In both seasons, the EC concentration did not change appreciably, whereas the OC concentration decreased at the rate of 0.10 μg C m−3 yr−1 in spring and 0.11 μg C m−3 yr−1 in winter. The OC/EC ratio was used to assess the importance of the sources of carbonaceous aerosol—biomass burning, fossil-fuel combustion, and air-pollutant transport from China—and the annual average OC/EC ratio was found to decrease from 5.7 to 2.4. The increasing contribution of fossil-fuel combustion is responsible for the decrease in OC derived from biofuel consumption transported from China to CHAAMS.

Keywords: Carbonaceous aerosol, CHAAMS, Fossil fuel combustion, Biomass burning, Long term trend

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